Grate assemblies for refuse incinerators



United States Patent GRATE ASSEMBLIES FOR REFUSE INCINERATORS 17 Claims, 6 Drawing Figs.

U.S.Cl

lnt.Cl

Field ofSearch 110/39 F23b 1/22 l 10/39; l26/l 76 Primary Lxaminer- Kenneth W. Sprague An0rneyWard, McElhannon, Brooks & Fitzpatrick ABSTRACT: An improved grate assembly for a movable grate incinerator having alternate movable and fixed grate sections. The fixed grate sections are provided with a frangible zone or area such that, if an unburnt refuse material becomes entrapped between the movable and fixed sections, controlled breakage occurs along the frangible zone of the fixed sections thereby minimizing possible damage to the movable grate sections or their associated supported drive mechanisms. Also, the grate sections are provided with cooperating tongue and groove contours to provide a nonlinear space therebetween to minimize the possibility of the unburnt refuse slipping therebetween.

Patented Dec. 1, 1970 Sheet Patnted Dec. 1, 1970- Sheet I (IRATE ASSEMBLIES FOR REFUSE INQINERATORS The present invention relates to grate assembliesfor refuse incinerators and more particularly to the grate assemblies for the so-called rocker or movable grate furnaces.

In refuseincinerators or furnaces having movable grate assemblies, one type of such grate assembly utilizes rockable or pivotable grate sections generally formed alternately of fixed and pivotable grate bars. The refuse to be burnt is deposited at the top end of the grate assembly which is usually inclinedand then it is advanced along the length of the grate assembly stepwise by pivoting or rocking the movable grate bars. Rocker grate furnaces of the type described, however, have been beset by a number of problems related to the movement of the movable grate bars. One of these problems relates to hard, unburnt refuse material which sometimes becomes entrapped between the pivotable bars and the fixed bars of the grate during movement of the pivotable bars. Such entrapped refuse may cause damage to the grates themselves or the movable grate bar support and drive mechanisms.

Likewise, clearance between adjacent movable and stationary grate bars is preferably kept to a minimum in the movable grate furnace of the present invention so as to minimize the amount and size of siftings that fall through the grate into the siftings hoppers below the grate assembly. Therefore, refuse should be totally incinerated so that these siftings are minimized thereby decreasing the handling and disposal thereof. This handling and disposal of siftings complicates the design and operation of the refuse incinerator plant. Minimizing the clearance also effects an increase in the velocity of the under grate air as it passes upwardly through the grate thereby producing more complete combustion of the refuse.

Preferably, the movable grate section of the furnace of the present invention comprises a single rocker bar pivotably mounted for rotation about an axis transverse to the longitudinal axis of the furnace grate and having mounted thereon along the length of the rocker bar a plurality of movable grate elements or teeth closely spaced one from another. These movable grate elements preferably extend on either side of the rocker bar and are provided with a forward end surface and a back end surface each of which is' closely spaced from an adjacent cooperating fixed bar element. The fixed bar elements are mounted transverse to the grate assembly and support a single grate element or a plurality of fixed grate elements corresponding generally to the number of movable elements.

In the preferred embodiment, the fixed elements also have a leading edge and a trailing edge closely spaced from their associated adjacent movable grate members and in each fixed element there is provided two frangible or weakened zones located adjacent respectively its trailing and leading edges to thereby cooperate with adjacent surfaces of their respective movable grate elements.

The function of the weakened or frangible zone is to permit controlled breakage of the fixed bars when hard unburnt refuse is trapped between the movable grate bar sections and the fixed grate bar sections during pivotal movement of the movable grate sections. The weakened or frangible zones of fixed or stationary bars provides a safety factor when unburnt refuse become thus entrapped since the fixed bars generally will break along the frangible zones thereby preventing damage to the more expensive movable bars or their as sociated support and drive mechanisms. Another problem which has been present in movable grate furnaces is that thin metal parts such as can lids and the like, normally found in refuse tend to slip between the grate bars and drop down below the grate with the siftings instead of being advanced along the length of the grate assembly and deposited at the end with the incinerated material. a

To overcome this, at least two of the movable grate bars of the furnace of the present invention are contoured in an intercooperating valley and ridge" arrangement. This arrangement while maintaining the spacing between the grate bars at a desired consistent but nonlinear distance thereby preventing passage of any flatlunburnt material having 'a thickness less than the spacing through the grate assembly into the sifting hoppers. If desired, the fixed and movable grate bar sections can be similarly mutually contoured to cooperate with each other to prevent slippage therebetween of such flat unburnt material.

Therefore, the object of the invention is to provide a new and novel movable grate assembly.

Other objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom or may be learned by practice with the invention, the same being realized and obtained by means of the instrumentalities and combinations pointed out in applicants claims.

The invention consists in novel parts, construction, arrangements, combinations and improvements herein shown and described.

The accompanying drawings referred and constituting a part hereof illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.

FIG. 1 is a longitudinal cross-sectional elevation of a portion of a grate constructed in accordance with the present invention;

FIG. 2 is a plan view of a portion of the grate illustrated in FIG. 1;

FIG. of a portion of the grate shown in FIG. 2;

FIG. 3 is a modified form of the grate shown in FIG. 2;

FIG. 3A is a modified form of the grate shown in FIG. 2A; and

FIG. '4 is a perspective view of a movable grate element shown in FIGS. I and 3.

Referring to the drawings and specifically to FIG. I, there is illustrated therein a grate assembly section designated generally G, embodying the present invention. Grate assembly section G may be part of a so-called batch type movable grate incinerator which usually has a single grate assembly section G or alternatively it may be part of a continuous type incinerator having a plurality of grate assembly sections G in a number of banks. The incinerator may be composed of one or, as is usually the case, a number of adjacent grate assemblies G. However, for simplicity of illustration and explanation, only a single grate, assembly G, is shown.

Normally the grate assembly G is inclined as shown in FIG. 1 with refuse material to be incinerated being travelled stepwise from the highest elevation on the grate assembly toward the lowest grate assembly elevation or from left to right as viewed in FIG. 1. In the continuous-type incinerator, a hopper (not shown) is provided which is kept full of refuse material which is fed out from the lower end of the hopper (not shown) by operation of the movable grate bar section directly there beneath. As the movable grate sections are operated, the refuse material is gradually raised and pushed forward along the grate assembly G, the raising of the refuse material having the tendency to break up the material and to allow for the passage of air therethrough to facilitate incineration.

Turning to FIG. 1, grate section G comprises movable grate bar sections, designated generally MB, and alternate fixed grate bar sections, designated generally P8. In the embodiment shown in FIGS. 1-3, the movable bar sections MB preferably each comprise a series of adjacent grate elements or teeth I mounted in common on a rocker bar 2 in turn pivotally mounted about an axis 3 generally transverse to the longitudinal axis of the grate assembly G. Preferably thirteen grate elements or teeth 1 are mounted on each rocker bar 2. It will be understood, however, that a greater or lesser number of teeth can be employed in connection with the present invention and, as in some traveling grate furnaces, even a single movable bar unit may be employed which is substantially the entire width of the grate section G. 7

Referring to the drawings, teeth 1 are each provided with a forward end surface 4 and a backward end surface 5 each of which is arcuate and rotatable about the axis 3. Each tooth 1 is also provided with an intermediate flat or refuse-supporting 3 surface 5a. The teeth 1 are preferably sector-shaped and as those teeth I. illustrated in the drawings are intermediate the side ends of the movable grate section MB. The intermediate teeth I as illustrated are preferably formed with an aperture 6 whereas the end teeth (not shown) of each movable grate section MB are formed without the aperture.

Between each movable grate section MB is a fixed grate section F B comprising a stationary or fixed mounting bar 7 which supports the stationary grate element 8. Each grate element 8 has a trailing edge 9 and a leading edge 9 which are closely spaced as shown in FIG. I3, from the forward end surface 4 and the backward end surface 5 respectively of the corresponding teeth I of the two adjacent members of the movable bar sections MB. Preferably the gap or space there between is of a very small distance of approximately one-sixteenth of an inch. As discussed herein above this space is kept to such a small dimension to reduce the amount and size of siftings that fall through the grate assembly G into the sifting hopper therebelow (not shown). Likewise, the narrow gap or space therebe'tween tends to increase the velocity of the under grate air as it passes through the grate assembly G, thereby providing efficient, controlled and even combustion.

Each stationary grate element 8 can be a single element substantially the entire width of the grate assembly G as shown in FIG. 2A or can comprise a plurality of stationary bars corresponding generally to the width of their associated movable teeth I, as shownin FIG. 2. Each fixed or stationary element 8 however is provided with at least one and preferably two weakening zones or frangible sections l0 and II.

Grate assembly G is constructed and arranged such that the movable bar sections MB are rocked alternately from left to right as shown in FIG. 1 so as to travel the refuse to be incinerated from the highest point on the grate section G toward the lowest point. The rocking motion or movement is imparted to the rocker bars 2 and thus to the movable bar sections MB preferably from an hydraulic power and cylinders (not shown). However, if desired mechanical linkage comprising cams and levers can be employed with equal facility.

One of the cylinders (not shown) drives a link 12, reciprocating drive bar 13. Drive bar 13 in turn is connected to every alternate rocker bar 2 by a second link 14. The remaining rocker bars 2 are driven 90 out of phase with the bars associated with link 12 by a similar drive arrangement (not shown), from a second hydraulic cylinder (not shown). It will be understood that any drive mechanism may be suitable for use in this invention which alternately rocks successive movable grate sections MB and 90 out of phase with successive movable bar section MB.

Turning specifically to FIG. 2, there is illustrated therein solely for illustrative purposes three teeth I and their adjacent stationary elements 8. It will be noted therein that the gap between the teeth I and the gaps between the end surfaces of the teeth and the elements 8 are all small preferably of the order of one-sixteenth of an inch. As pointed out hereinabove the minimizing of this distance compatible with proper clearance for movement of the movable teeth 1 permits a reduction of the amount of and size of the siftings that fall through the grate assembly and in addition effects an increase of the velocity of the under grate air as it passes through the grate assembly G and into contact with the material to be incinerated. It has been found that by maintaining the clearances to a minimum, efficient control and even combustion is obtained.

In operation, grate section G is preferably mounted in an inclined manner such as shown in FIG. I. Preferably this inclination is about 1 1 to the horizontal. The refuse to be incinerated is deposited on the uppermost grate assembly G and at the uppermost portion of the grate assembly. The refuse LII ble bar sections MB tends to agitate and break up the refuse facilitating its incineration.

When there are a plurality of grate sections G. in each of which are generally eight'movable bar units MB. the grate sections G are arranged preferably in banks with a vertical drop of between I and 3 feet between each section. Again such vertical drops tend to further facilitate the agitation and breaking up of the refuse for better incineration. Again, it will be understood that grate sections G may include a greater or lesser number of movable sections MB depending on the length of the grate.

As shown in FIG. I, the stationary bar elements 3 are provided with at least one and preferably two frangible or weakened sectionsor zones 10 and 11. Thus, should a piece of hard, unburnt material become entrapped between one of the movable teeth 1 and one of the stationary elements 8 during the pivotal movement of such teeth I as described hereinabove, the fixed bar element 8 will normally fracture along the adjacent weakened zone 10 or Ill thereby leaving tooth I usually undamaged. This is preferable to fracture of a tooth since, due to the configuration of the grate, such broken portion of element 8 falls below the grate assembly G, thus leaving only a small gap and no part to interfere with operation of the movable bar sections MB. Secondly, the fixed bar elements 8 are usually of cast iron which is a relatively inexpensive material as compared to the teeth I which are of a high quality steel. I

An additional feature of the present invention which utilizes a multiplicity of teeth I in preference to a single movable grate unit, is that if unburnt refuse material does cause a fracture of a tooth I, only a single tooth need be replaced. This is preferable to the commonly used grate arrangement in which a single casting comprises the entire movable bar section. Understandably, replacement of a single casting rather than just an individual tooth would be substantially more expensive and time consuming. Likewise, the frangible zones 10 and Ill reduce substantially the possibility of damage to the movable bar-support and drive mechanism from an entrapped refuse material. This is especially the case where the movable bar sections MB are comprised of a multiplicity of teeth I.

As shown best in FIG. 2, the fixed bar elements 8 can be comprised of a plurality of elements each of which has the width of its corresponding tooth 1. Damage due to hard unburnt material will result in only one or two of the fixed elements 8 having to be replaced rather than the entire fixed bar unit FB. However, the fixed bar section FB can include only a single element 8 such as shown in FIGS. 2A and 3A although the plurality of fixed bar elements 8 is preferred.

Turning to FIG. 3, there is illustrated therein another modification of the present invention which prevents thin pieces of unburnt refuse such as tin can lids from falling through the spacings of the teeth 1 and the elements 8. To accomplish this each tooth 1 is provided on the end surfaces 4 and 5 thereof with suitable ribs I5 and I6 respectively, which i'correspond with cooperating recesses l7 and 18 formed in the adjacent fixed bar sections 8. It will be understood that the nonlinearity of the gaps, the width of which still remains conjstant, reduces the chance of unburnt material such as can lids i ribbing and grooving I9 and 20 can be provided on adjacent material is then traveled stepwise along the grate assembly G by alternate rocking through preferably 90 of the movable I bar sections MB of the grate assembly G. It will be understood that the refuse is thus progressively propelled down the grate I assembly G. Likewise, therocking or movement of the moval teeth for the same purpose. (See FIGS. 3 and 3A).

The various ribs and grooves I9 and 20 on a grate tooth l are shown in FIG. 4. It will be understood that by the arrangement shown in FIGS. 3 and 3A the nonlinearity of the spaces or gaps between adjacent teeth 1 and their cooperating fixed bar sections 8 prevent a thin unburnt piece of refuse such as a tin can lid from slipping down between adjacent teeth or a tooth and its adjacent fixed bar element a into the siftings where it presents a problem in subsequent handling and disposing of siftings. As shown best in FIGS. 3 and 3A the nonlinear spacing continues to remain constant to provide for the necessary clearance for movement of the teeth I.

There is thus disclosed a new and novel and highly useful movable grate assembly for continuous grate refuse incinerators.

lclaim:

l. A grate assembly for use in a movable grate refuse incinerator comprising a plurality of alternate movable and stationary grate sections, means for supporting said sections in adjacent spaced relationship, means mounting said last-named means for disposing said grate sections in a downwardly inclined direction, means for intermittently moving said movable grate sections relative to said stationary sections whereby refuse is traveled stepwise downwardly along said assembly for incineration, and at least one frangible zone for each of said stationary sections adjacent a movable section whereby any unburnt refuse entrapped between a movable and stationary grate section causes a fracture in said stationary grate section along'its associated frangible zone thereby minimizing possible damage to said movable grate sections and their associated support and drive mechanisms.

2. The grate assembly of claim 1 wherein each stationary grate section is provided with two frangible zones one of which is located adjacent each movable section disposed on either side of said stationary section.

3. The grate assembly as defined in claim 1 wherein each movable grate section is comprised of a pluralityof teeth elements mounted for rockable movement relative to said stationary grate sections.

4. The grate assembly as defined in claim 3 wherein said stationary grate sections are comprised of a plurality of bar elements, one of which is associated with each tooth of said movable grate section.

5. A grate assembly for use me movable grate refuse incinerator comprising a plurality of alternate movable and stationary grate sections, said movable sections being formed of a plurality of teeth, and a rocker bar supporting said teeth in adjacent spaced relationship in common for rotation about an axis generally transverse to the longitudinal axis of said grate assembly, a frame supporting said movable and stationary grate sections in adjacent downwardly inclined relationship, drive means for each of said movable section rocker bars and means for selectively simultaneously actuating the drive means of alternate movable sections to pivot the teeth of said actuated sections about their associated axis transverse to the longitudinal axis of said grate assembly and thereby travel refuse stepwise downwardly along said grate assembly, and a frangible zone formed in each of said stationary sections adjacent a movable section whereby unburnt refuse entrapped between said teeth of a movable grate section and its adjacent stationary grate section during pivotal movement of said teeth cause a fracture in said stationary grate section along its frangible zone thereby minimizing possible damage to said movable grate sections and their associated support, drive and actuating means.

6. The grate assembly as defined in claim 5 wherein said stationary grate sections are comprised of a plurality of bar elements, one close which spaced associated with each tooth of said movable grate section.

7. The grate assembly as defined in claim 5 wherein air is provided beneath said grate assembly and said teeth are sup ported in close adjacent spaced relationship on their associated rocker bar and said movable and stationary grate sections are supported in said frame in close adjacent spaced relationship whereby the velocity of said air passing through said grate sections is increased as it moves through the close adjacent spacing of said teeth and said movable and stationary grate sections and the size of refuse siftings falling through said grate assembly during incineration is minimized.

S. The grate assembly of claim 5 wherein each stationary gratesection is provided with two frangible zones one of which is located adjacent each movable section disposed on either side of said stationary section.

9. A grate assembly for use in a movable grate refuse incinerator comprising a plurality of alternate movable and sta-- tionary grate sections. means for supporting said sections in parallel adjacent closely spaced relationship, means mounting said last-mentioned means for disposing said grate sections in a downwardly inclined direction, and means for intermittently moving said movable grate sections relative to said stationary sections whereby refuse is traveled stepwise downwardly along said assembly for incineration, said movable grate sections each being formed from a plurality of adjacent, closely spaced, tooth-like elements with cooperating ribs and grooves formed on confronting sides of said elements whereby the spaces between adjacent elements in each of said movable grates are nonlinear thereby minimizing the possibility of thin unburnt refuse slipping therebetween and through said grate assembly.

10. The grate assembly of claim 9 wherein said movable grate sections and said stationary grate sections are formed with cooperating ribs and grooves whereby the space between adjacent movable and stationary sections is nonlinear thereby minimizing the possibility of thin unburnt refuse slipping therebetween and through said grate assembly.

11. A grate assembly for use in a movable grate refuse incinerator comprising a plurality of alternate movable and stationary grate sections, said movable sections being formed of a plurality of teeth, and a rocker bar supporting said teeth in adjacent spaced relationship in common for rotation about an axis generally transverse to the longitudinal axis of said grate assembly, a frame supporting said movable and stationary grate sections in adjacent downwardly inclined relationship, drive means for each of said movable section rocker bars and means for selectively simultaneously actuating the drive means of alternate movable sections to pivot the teeth of said actuated sections about their associated axis transverse to the longitudinal axis of said grate assembly and thereby travel refuse stepwise downwardly along said grate assembly, and cooperating ribs and grooves formed on confronting sides of adjacent teeth of each of said movable grate sections whereby the space between said adjacent teeth is constant but nonlinear thereby providing clearance therebetween while minimizing the possibility of thin unburnt refuse slipping therebetween and through said grate assembly.

12. The grate assembly of claim 11 wherein said movable grate sections and said stationary grate sections are formed with cooperating ribs and grooves whereby the space between adjacent movable and stationary sections is nonlinear thereby minimizing the possibility of thin unburnt refuse slipping therebetween and through said grate assembly.

13. The grate assembly as defined in claim 12 wherein said stationary grate sections are comprised of a plurality of bar elements, one of which is associated with each tooth of said movable grate section.

14. A grate assembly for use in a movable grate refuse incinerator comprising a plurality of alternate movable and stationary grate sections, means for supporting said sections in adjacent spaced relationship, means mounting said last-named means for disposing said grate sections in a downwardly inclined direction, means for intermittently moving said movable grate sections relative to said stationary sections whereby refuse is traveled stepwise downwardly along said assembly for incineration, at least one frangible zone for each of said stationary sections adjacent a movable section whereby any unburnt refuse entrapped between a movable and stationary grate section causes a fracture in said stationary grate section along its associated frangible zone thereby minimizing possible damage to said movable grate sections and their associated support and drive mechanisms and cooperating ribs and grooves formed on adjacent movable and stationary grate sections whereby the space between adjacent movable and stationary sections is nonlinear thereby minimizing the possibility of thin unburnt refuse slipping therebetween and through said grate assembly.

15. The grate assembly of claim 14 wherein said movable grate sections comprise a plurality of adjacent spaced elements and cooperating ribs and grooves formed on said adjacent spaced elements whereby the space between-said adjacent elements is constant but nonlinear thereby providing clearance between said adjacent elements while minimizing the possibility of thin unburnt refuse slipping therebetween.

16. A grate assembly for use in a movable grate refuse incinerator comprising a plurality of alternate movable and stationary grate sections, said movable sections being formed of a plurality of teeth, and a rocker bar supporting said teeth in adjacent spaced relationship in common for rotation about an axis generally transverse to the longitudinal axis of said grate assembly, a frame supporting said movable and stationary grate sections in adjacent downwardly inclined relationship, drive means for each of said movable section rocker bars and means for selectively simultaneously actuating the drive means of alternate movable sections to pivot the teeth of said actuated sections about their associated axis transverse to the longitudinal axis of said grate assembly and thereby travel refuse stepwise downwardly along said grate assembly, a frangible zone formed in each of said stationary sections adjacent a movable section whereby unburnt refuse entrapped between said teeth of a movable grate section and its adjacent stationary grate section during pivotal movement of said teeth cause a fracture insaid stationary grate section along its frangible zone thereby minimizing possible damage to said movable grate sections and their associated support, drive and actuating means and cooperating ribs and grooves formed on adjacent teeth of each of said movable grate sections whereby the space between said adjacent teeth is constant but nonlinear thereby providing clearance therebetween while minimizing the possibility of thin unburnt refuse slipping therebetween and through said grate assembly.

17. The grate assembly of claim 16 wherein said stationary grate sections are comprised of a plurality of bar elements, one of which is associated with each tooth of said movable grate section and each bar element of a stationary grate section is provided with two frangible zones one of which is located adjacent each tooth of the movable section disposed on either side of said bar element and cooperating ribs and grooves formed each tooth and its associated bar elements whereby the space therebetween is nonlinear thereby minimizing, the possibility of thin unburnt refuse slipping through said grate assembly.

2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 140. 35434703 Dated 12ec emner l.. l9l0 Invent 1( Gpoffrev Alan Archer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[ Page [11] [73] Assignee "Nicholas" should read Nichols-- Col 2 line 26 after "FIG (first occurrence) insert -2A is a plan view of another embodiment-- Col 3 line 48 after "MB" insert simultaneouslymazes) m smuzn RAM 1971 G Am zdwnrdnl 'ladzenln mm B. 11 3- Officer dominion of MB 

